1. Field of the Invention
The invention relates to a computer management system and, more particularly, to a computer management system having plural instrumentation agents for querying manageable devices to collect object data and an associated enterprise management information base (or "MIB") for storing object data in accordance with a specified MIB architecture.
2. Description of Related Art
The Internet community has defined an organizational framework of data and provides a naming authority allowing any company or group to define information within the framework in a way that allows any or all of this data to coexist. Under the control of the International Telegraph and Telephone Consultative Committee (or "CCITT") and the International Organization for Standardization (or "ISO"), the organizational framework has been constructed as a tree. The root of the tree is managed by CCITT and ISO. Extending from the root of the tree are a series of branches defined by CCITT and ISO. However, while the branch is initially defined by the managing authority, authority for the branch may then be given to another organization for defining the child branches for that branch. FIG. 1 illustrates the structure of the organizational framework defined by the Internet community and is included here so that the relationship of the enterprise MIB subject of the present application and the remainder of the Internet community will be clear.
Every piece of information within the organizational framework is configured in a formal grammar and referred to by its full name so that it can be unambiguously specified, thereby making information transfers within an interoperable network system possible. A series of dotted decimal notations, each separated by periods, specifies all of the branches needed to reach a particular item. For example, all items originating in a private enterprise would be headed by the notation "1.3.6.1.4.1". From a specific private enterprise, an item would be identified using the name 1.3.6.1.4.1.XXX.YY where "XXX" is an identifier assigned to that enterprise by the ISO and "YY" is an identifier assigned to that particular item by enterprise "XXX" under the authority of the ISO.
Simple Network Management Protocol (or "SNMP") is a protocol widely used within the Internet community for interoperable network management The SNMP protocol defines a set of commands that a management application may use to retrieve or change the value of items that a management agent is making available. The Internet community also maintains a series of documents which describe the communication protocols used by the community. These documents are called "Request for Comments" and are commonly referred to as "RFCs". Each RFC is assigned a number to identify the document. For example, RFC 1212 defines the formal grammar for a SNMP MIB.
A MIB is a data base that describes a set of items that management applications and agents use to report and control managed devices. A description of a MIB starts with a line that states the name of the MIB being defined. Typically, the name of the MIB is followed by an import statement which allows the MIB writer to specify information from other well known MIBs that are referred to in the MIB being defined. Within a MIB is a structure for organizing managed items. To form the structure, the MIB defines a group or groups for organizing related pieces of information. A group is defined by stating a name for the group and showing how the group fits into the tree. Typically, all group definitions are placed immediately following the IMPORTS statement. Groups may contain information in the form of items or "objects", sub-groups, or a combination of the two. Similarly, each sub-group is configured like a group.
Within a group or sub-group, data may be organized in one of two basic methods. A scalar item is a single piece of information that is within a group. For example, the total memory in a server is a scalar item. A table is a structure for organizing data that requires more information to uniquely identify a single data item within a group of similar items. An example of an item that is best organized in a table is an EISA board ID. It is necessary for someone requesting an EISA board ID to specify the EISA board to which they are referring.
Each item, either scalar or part of a table, defined in a MIB includes a description which explains the item. Typically, the description includes SYNTAX, ACCESS, STATUS and DESCRIPTION clauses. The SYNTAX clause specifies the type of information which the item contains. Information types typically specified by the SYNTAX clause include INTEGER, OCTET STRING, Counter and DisplayString. INTEGER specifies that the value of the item should be interpreted as a number. OCTET STRING specifies that the value of the item should be interpreted as a string of octets, each having a value between 0 and 255. Counter specifies that the item is an INTEGER that has an implied range of zero to FFFFFFFF. DisplayString specifies that the item is an OCTET STRING where each octet is restricted to a printable ASCII character.
The ACCESS clause specifies the ways the item may be used and shows the actions which the agent may support for the item. ACCESS may be read-only, read-write or not-accessible. Read-only means that the value of the item may be retrieved by a management application but may not be altered. Read-write means that the item may be read and/or altered by a management application. Not-accessible is given as the access for organizational constructs that do not represent data items. Not-accessible is used only for table features and should not be used for a scaler item. The STATUS clause specifies whether the item is required for an agent that supports the defined group. A STATUS of mandatory means that the item will always be present if the defined group is supported by the agent. A STATUS of optional means that a particular implementation has the option of supporting the item. The DESCRIPTION clause contains a double quote delimited text description of the item. Finally, the item definition ends by specifying how the item fits into the MIB tree. The group the item belongs to is given, followed by the unique branch number within the group for the item.
To organize a table requires the use of two additional operators, the SEQUENCE operator and the SEQUENCE OF operator. The SEQUENCE operator allows the definition of a new type that consists of several standard types in a specific order. The SEQUENCE OF operator allows the definition of a list of zero or more of the same type of elements. A table is formed by defining a SEQUENCE, typically called a table entry. A table is defined as a SEQUENCE OF the table entry type. As there is no data that is uniquely referred to by the name of the table or entry, the STATUS of the table and the table entry is not-accessible. The INDEX clause specifies the items that can be used to uniquely identify an element in the table.
A MIB may also contain trap definitions. A trap is a notification sent by the SNMP agent to a management console. The trap is sent to inform the management console about an event that has occurred on the managed system. The trap definition begins with the name of the trap, followed by the term TRAP-TYPE. An ENTERPRISE clause follows to indicate the MIB in which the trap is defined. An optional VARIABLES clause may also be included to specify additional information that will be sent in the trap. Typically, the additional information contained in the VARIABLES clause will be items defined in the MIB identified in the ENTERPRISE clause. A DESCRIPTION clause which explains the significance of the trap and the conditions that would cause it to be sent follows. Finally, the trap is given a number to identify it. The number will be unique within the scope of the ENTERPRISE. Both the enterprise name and the trap number are used by the management station to uniquely determine the identity of a received trap.